The present invention relates to a digital signal up-converting apparatus and related digital signal up-converting method, and more particularly to a low cost, low power, and low spurs digital quadrature converter and related method.
In wireless communication system, using a digital polar transmitter to transmit RF (Radio Frequency) signal is the most area saving and power efficient way. However, this conventional method needs a high clock rate CORDIC (Coordinate Rotation Digital Computer) that consumes large area and digital power. Moreover, by using the digital polar transmitter, a mechanism is also need to provide for truncating the ultra-wide bandwidth frequency signal when the signal bandwidth increases. In other words, this mechanism degrades the EVM (Error Vector Magnitude) of the transmitted signal when the signal bandwidth increases. Another conventional way to transmit the RF signal is to directly convert the baseband data IQ in RF signal by a DAC (Digital-to-analog Converter), which is so-called I/Q RF DAC. The I/Q RF DAC is good for maintaining signal integrity of the transmitted signal. However, the I/Q RF DAC requires double silicon area to deliver the same amount of power in comparison to the digital polar transmitter counterpart. Therefore, providing a low cost, low power, and high bandwidth digital transmitter is an urgent problem in the field of wireless communication system.